The quenching of nonwoven filaments using air and other fluids is known in the art. U.S. Pat. No. 3,070,839, issued to Thompson, discloses using a stream of air to quench melt spun filaments. A screen is positioned between the air supply and the filaments to diffuse the air stream and minimize its turbulence. The cooling is accomplished in zones ranging from relatively low air flow near the spinnerette to successively greater air flows at distances further from the spinnerette. This technique allegedly reduces the breakage of filaments during cooling.
U.S. Pat. No. 4,492,557, issued to Ray et al., discloses the use of diffusers to reduce turbulence of cooling gas. The turbulence-reducing diffusers disclosed include screens, porous foam, perforated metal plates, sintered metal, metallic wool, felt, and sandwiches of meshed screens. A varied gas distribution pattern can be achieved by providing a diffuser having regions of different porosity.
U.S. Pat. No. 4,712,988, issued to Broaddus et al., discloses an apparatus for radially quenching melt spun filaments. A quenching chamber is provided with a foraminous distribution cylinder between the filaments and the gas supply. Quenching gas enters the cylinder from all sides, and is diffused by the foraminous cylinder. The foraminous openings are sized to control the velocity of the quenching gas entering the filaments.
The use of flow control devices, namely gas diffusers, has generally been for the purpose of reducing gas velocity and turbulence. These techniques distribute and diffuse the gas flow and are intended to introduce a more tranquil, laminar flow having less tendency to disturb or break the filaments. However, the nature of laminar flow is such that when quenching gas (e.g., air) contacts the filaments, the rates of heat transfer and quenching are relatively lower. There is a need or desire in the nonwoven industry for a quenching technique which optimizes cooling efficiency as well as evenly distributing the gas.